This invention relates to a catalyst composition, the preparation of a catalyst composition, and to a process of using a catalyst composition for hydrogenating a highly unsaturated hydrocarbon.
It is well known to one skilled in the art that an unsaturated hydrocarbon can be produced by a thermal cracking process. For example, a fluid stream containing a saturated hydrocarbon such as, for example, ethane, propane, butane, pentane, naphtha, or combinations thereof can be fed into a thermal (or pyrolytic) cracking furnace. Within the furnace, the saturated hydrocarbon is converted to a less unsaturated hydrocarbon such as, for example, ethylene and propylene. Less unsaturated hydrocarbons are an important class of chemicals that find a variety of industrial uses. For example, ethylene and propylene can be used as a monomer or comonomer for producing polyolefins. Other uses of less unsaturated hydrocarbons are well known to one skilled in the art.
However, a less unsaturated hydrocarbon produced by a thermal cracking process generally contains an appreciable amount of highly unsaturated hydrocarbons such as less desirable alkyne(s), diolefin(s), polyene(s), or combinations thereof. For example, ethylene produced by thermal cracking of ethane is generally contaminated with some acetylene which must be selectively hydrogenated to ethylene, but not to ethane, in a hydrogenation reaction. Similarly, in a thermal cracking process for producing a butene, butynes and butadienes are generally co-produced which must be selectively hydrogenated to a butene, but not further hydrogenated to a butane.
These highly unsaturated hydrocarbons described above are undesirable for several reasons. Generally, these highly unsaturated hydrocarbons are highly reactive and tend to polymerize by forming gums if they are left in the product stream. Also, these undesirable products can have an effect on further processes, such as alkylation. Thus, these highly unsaturated hydrocarbons are preferably removed. A preferred process for removing such undesirable highly unsaturated hydrocarbons is a selective hydrogenation process. This process not only minimizes the loss of desired less unsaturated hydrocarbons, but can also help to avoid a "runaway" reaction which is difficult to control in front-end and total-cracked-gas processes thereby increasing the selectivity by which desired products, as opposed to undesired products, are produced.
Catalysts comprising palladium and an inorganic support are known catalysts for the hydrogenation of highly unsaturated hydrocarbons such as alkynes and/or diolefins. Sulfided catalysts comprising a metal selected from the group consisting of molybdenum, cobalt, and nickel and combinations thereof have also been used as hydrogenation catalysts. However, these catalysts can be expensive to prepare and can have the potential to introduce sulfur contaminants which can poison and deactivate catalysts used in hydrogenation processes.
As such, development of a catalyst which is cost-efficient and easier to prepare than known catalysts and processes therewith in the selective hydrogenation of a highly unsaturated hydrocarbon such as a diolefin to a less unsaturated hydrocarbon such as a monoolefin in which selectivity is improved and unnecessary introduction of contaminants is avoided would be a significant contribution to the art and to the economy.